If you're one of those people who strongly identifies with those "But First, Coffee" t-shirts they sell at Target, your DNA might be to blame. No, not for the fact that you're 32 and still buying t-shirts at Target, but for your general coffee addiction—because a team of scientists has discovered what appears to be a connection between coffee consumption and one oddly specific genetic variation.
In a recent study, researchers from the University of Edinburgh examined the coffee-drinking habits of 1,207 villagers in both Northern and Southern Italy and discovered that those who had a variation in a gene called PDSS2 drank fewer cups of joe than the caffeine-fiends who did not have that particular variation. The difference between the two groups was the equivalent of one cup of coffee per day. They then replicated the study with an additional 1,731 participants in the Netherlands, with the same—if less emphatic—results. (The authors did exclude any Dutch person who drank more than 20 cups of coffee per day, possibly because they couldn't stop vibrating long enough to answer the survey).
In the study, which was published in the journal Scientific Reports, the researchers suggest that PDSS2 regulates the body's ability to metabolize caffeine. Those who have the genetic variation—and who aren't refilling their cups as often—break caffeine down more slowly, which means they feel the effect of coffee longer than the rest of the population. So if your Starbucks order is less tall than Venti, you might have standard-issue PDSS2. (And it's on chromosome 6, if you want to untangle your own DNA at home).
Even though the researchers reached the same conclusions after studying both groups, why was the difference more pronounced in the Italians? Interestingly, they believe it's because of the way the two countries take their coffee. "While in Italy, moka or espresso are the preferred way of drinking coffee, in the Netherlands, filtered coffee is preferred," lead author Nicola Pirastu wrote. "Although the concentrations of caffeine in the different preparation methods are similar, given the differences between cup sizes, Dutch intake of caffeine per cup is almost three times higher than Italians."
Pirastu believes that the study has discovered a link between PDSS2 and coffee cravings, but says that additional research is needed to understand the biological mechanism that connects the two. "We believe to have added an important piece to the understanding of the genetic basis of coffee consumption and potentially to the mechanisms regulating caffeine metabolism," he wrote.
Before he starts working on that paper he, should probably brew a pot of coffee. Or ten.